Adapted from recipe published in Saveur magazine, December 2009. Black and brown mustard seeds are used in Asian cooking; they impart a different flavor than yellow mustard seeds.
In a bowl, combine paprika, coriander, turmeric, and garlic powder; set aside. Heat oil in a 4-quart saucepan over high heat. Add mustard seeds. Cook until fragrant, about 3 minutes.
Add reserved spice mixture, chiles, cauliflower, and water and cook until tender, 5-6 minutes.
Lower heat to medium, add tomatoes, and season with salt; cook, covered, until softened, about 2 minutes.